From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Neon Absentius Newsgroups: gmane.emacs.help Subject: Re: Non-Commutative calculations in Calc, Revisited Date: Thu, 6 Oct 2005 18:01:13 +0000 Message-ID: <20051006180113.GA24696@SDF.LONESTAR.ORG> References: <878xx66b1c.fsf@vh213602.truman.edu> <851x2yu5gv.fsf@lola.goethe.zz> NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1128621878 13259 80.91.229.2 (6 Oct 2005 18:04:38 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Thu, 6 Oct 2005 18:04:38 +0000 (UTC) Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Oct 06 20:04:25 2005 Return-path: Original-Received: from lists.gnu.org ([199.232.76.165]) by ciao.gmane.org with esmtp (Exim 4.43) id 1ENa4G-00048a-6T for geh-help-gnu-emacs@m.gmane.org; Thu, 06 Oct 2005 20:02:08 +0200 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ENa4F-0008NA-IC for geh-help-gnu-emacs@m.gmane.org; Thu, 06 Oct 2005 14:02:07 -0400 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1ENa41-0008N5-Ae for help-gnu-emacs@gnu.org; Thu, 06 Oct 2005 14:01:53 -0400 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1ENa3z-0008Ms-Re for help-gnu-emacs@gnu.org; Thu, 06 Oct 2005 14:01:53 -0400 Original-Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ENa3z-0008Mp-M2 for help-gnu-emacs@gnu.org; Thu, 06 Oct 2005 14:01:51 -0400 Original-Received: from [192.94.73.21] (helo=sdf.lonestar.org) by monty-python.gnu.org with esmtp (Exim 4.34) id 1ENa3y-0006Xq-UK for help-gnu-emacs@gnu.org; Thu, 06 Oct 2005 14:01:51 -0400 Original-Received: from sdf.lonestar.org (IDENT:absent@ukato.freeshell.org [192.94.73.7]) by sdf.lonestar.org (8.13.1/8.12.10) with ESMTP id j96I1D3W011209 for ; Thu, 6 Oct 2005 18:01:13 GMT Original-Received: (from absent@localhost) by sdf.lonestar.org (8.13.1/8.12.8/Submit) id j96I1DKH026403 for help-gnu-emacs@gnu.org; Thu, 6 Oct 2005 18:01:13 GMT Original-To: help-gnu-emacs@gnu.org Mail-Followup-To: Neon Absentius , help-gnu-emacs@gnu.org Content-Disposition: inline In-Reply-To: <851x2yu5gv.fsf@lola.goethe.zz> User-Agent: Mutt/1.4.2.1i X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:29991 Archived-At: On Thu, Oct 06, 2005 at 03:42:40PM +0200, David Kastrup wrote: > Jay Belanger writes: > > > Neon Absentius writes: > > > >> When in non-commutative (aka `matrix') mode calc calculates > >> (a b)^-1 to be a^-1 b^-1 instead of the correct b^-1 a^-1. > > Uh, what's correct about b^-1 a^-1? > > Set a=[1,1], b=[1;0], then (a b)^-1 = [1], and neither b^-1 nor a^-1 > exist. > > This only works with a and b being square matrices. Yes you are right. However I am more interested in the case that there is a *globally* defined associative multiplication and I am using the matrix mode as a "poor man's no-commutative algebra mode". In this context my remark makes sence. I still believe that there is a need for such a mode, perhaps a "sub-mode" of the matrix mode where one assumes that all matrices are square. I am not sure how hard this is to implement. What do you think Jay? -- Everyone is so overwhelmed by the hospitality. And so many of the people in the arena here, you know, were underprivileged anyway, so this--this (she chuckles slightly) is working very well for them. -- Barbara Bush, about the refugees from New Orleans.